In U.S. Pat. No. 4,385,507, a yarn changing striper box apparatus for a circular knitting machine is provided with selection units which rotate synchronously with the needle cylinder around the axis of the knitting machine. A plurality of yarn feeding fingers are arranged side-by-side and are selectively moved by the selection unit between an operative position at which yarn feeding to the needle is performed and a nonoperative position at which yarn feeding is terminated. The selection unit is controlled by a remote program, which in turn energizes a pair of solenoids. Each solenoid includes a raising cam and lowering cam along an axis thereof. The cams raise and lower jack selection members by engaging selection butts on the selection members. A three-arm rocking lever is positioned adjacent to the selection unit. The first arm of the three-arm lever is connected to the yarn feeding finger. The second arm is connected to a jack selection member. The third arm is resiliently provided with a claw for operating a cutter. During termination of yarn feeding, a yarn end catcher having moveable and unmovable blades is actuated by the claw and a rotating cam supported by the selection unit. The yarn end held thereby is cut at the time of yarn feed switching.
Although the aforementioned device offers several benefits over many existing prior art devices, this apparatus has several drawbacks. The upper and lower cams positioned on the solenoid axis which raise and lower the jack selection members are not efficient because of the linear movement imparted thereto. The selection speed provided in the apparatus is low and during speed-up of the knitting operation, efficiency is lost. Additionally, the linear movement of the solenoids mandate that a large circumferential area of the knitting machine is set aside for the solenoids. Thus, &he machine is not as compact as desired.